Electronic or computer systems employ multiple memory types, which may be grouped according to volatile and non-volatile capabilities. Non-volatile memory types retain stored data even when no electrical power is being supplied to the electronic system. Electronic systems may include various types of non-volatile memory devices such as disk drives including magnetic drives commonly referred to as “hard drives.” Disk drive systems typically excel in the ability to store and retrieve large quantities of data. Hard drive form factors have evolved to include portable removable media such as memory cards, memory sticks, Flash cards and Flash drives. Due to their portable nature, these types of memories include electromechanical interface components that may be timely or untimely disconnected from their host system or otherwise have their power source untimely interrupted. Furthermore, these removable non-volatile memory devices often incorporate data retention technology that is sluggish in writing or programming data to the storage medium. Accordingly, the probability that a power interruption may occur when data is being written to the memory device is significant enough to require attention.
A file allocation table (FAT) is associated with the storage media in order to be able to determine which data was written to the medium, and to be able to determine a place on the medium where the stored data is located. Several different kinds of FAT standards have been developed, including FAT12, FAT16 and FAT32, to address needs of different systems. In a conventional FAT file system, new data or changes to an existing file are written over and/or appended to a previous version of the file when a file is modified. Following writing of the new data or changes, the FAT is updated providing the memory device remains attached and powered. However, a conventional FAT file system is vulnerable to corruption from an interrupted write or programming operation of the memory device resulting from, for example, an intervening power loss such as when the memory device or the power source to the memory device is prematurely disconnected.
Should a power interruption occur after initiation of a write of new data to a file, but before or during the corresponding FAT write operation, the entire file system can be damaged or destroyed. While the likelihood of a complete file system loss is small, there is a large probability of lost data segments configured as cluster chains that may or may not be recoverable following restoration of power to the device. Conventional FAT file systems, by design, are not transaction-safe file systems. The conventional FAT can be corrupted when a write or programming operation is interrupted during a file editing process resulting in corruption of a file or entire loss of some data within the file.
For the reasons stated above, and for other reasons stated below which will become apparent to those of ordinary skill in the art upon reading and understanding the present specification, there is a need in the art for improved non-volatile memory devices.